Ten clinical centers in the United States are recruiting cases for an NIH sponsored study titled "A Case Control Etiologic Study of Sarcoidosis." The objectives include: 1) to test hypotheses concerning environmental, occupational, lifestyle, and other risk factors for sarcoidosis, 2) examine the familial aggregation of sarcoidosis, 3) To test genetic hypotheses concerning aggregation of sarcoidosis, 4) To describe the natural history of sarcoidosis, particularly among groups such as African-Americans who appear to be disproportionately affected, 5) To identify risk factors for progression to more sever disease and 6( To implement a system for storing biological specimens including blood cells, plasma, and serum from cases and control subjects and bronchoalveolar lavage fluid and cells from a well characterized series of cases of sarcoidosis which represent the spectrum from mild to severe disease.